The present invention relates to an ion beam apparatus which changes wiring, or metallization, in an IC by ion beam etching or deposition of metal film thereon, and particularly to an ion beam apparatus which further functions as an IC tester for measuring a potential of a sample by irradiating an ion beam on the sample and analyzing energy of secondary electrons generated from the sample.
The density and size of wiring in an IC are further being miniaturized at a drastic rate. In order to promote and assist such drastic technology improvement, appropriate device verification technology and device malfunction analysis technology are indispensable. In the prior art technology, a pointed tungsten probe coupled to an oscilloscope is directly contacted to an IC device to measure internal signals thereof. This method is almost impossible to apply to the measurement of a VLSI because it is extremely difficult to position the very fine probe to an extremely fine target point. In order to overcome this difficulty, an electron beam (EB) tester was invented as a replacement of the conventional tester, whereby the measurement of signals at a miniaturized pattern has become possible.
However, even this method is not effective enough to apply to an IC device having wiring routes in multiple layers, nor can this method apply when there is a passivation film deposited over an IC device. Again, in order to solve these problems, a focused ion beam apparatus was invented. The apparatus can carry out various tasks, such as drilling a hole through a passivation film deposited over wiring, and cutting wiring by ion beam etching; and connecting wiring, and forming a probing pad through a passivation film by forming a metal film by the use of an ion beam CVD method. Since this apparatus can drill a hole through a passivation film provided over the IC wiring patterns, and form probing pads, an EB tester can measure internal signals of an IC device. (Monthly Semiconductor World 1987. September "Novel verification and analysis of VLSI using FIB").
FIG. 2 schematically shows a well known EB tester. Numeral 1 denotes an electron beam, numeral 2 an objective lens, numeral 3 a scanning electrode, numeral 4 a grid electrode, numeral 5 an extracting electrode, numeral 6 a sample such as an IC, numeral 7 secondary electrons, numeral 8 a secondary electron detector, numeral 9 an amplifier, numeral 10 a comparator, numeral 11 a power source for grid electrode 4, numeral 12 a monitor, and numeral 13 a power source for extracting electrodes.
In the EB tester having such structure as described above, secondary electrons 7 generated from the sample 6 by the irradiation of the electron beam 1 are decelerated in a deceleration magnetic field between the extraction electrode 5 and the grid electrode 4, and only the secondary electrons which pass the grid electrode are detected by the secondary electron detector 8. A detected signal is amplified by the amplifier 9, and inputted into the comparator 10 at which the detected signal is compared with a reference signal. The power source 11 is controlled to adjust the potential of the grid electrode 4 so that the detected signal becomes the same level as that of the reference signal. Then the potential so adjusted is displayed on the monitor 12 such as an oscilloscope, or a recorder.
FIG. 3 shows a focused ion beam apparatus of the prior art. Numeral 21 denotes an ion source, numeral 22 an ion beam, numeral 23 a beam monitor, numeral 24 is a condenser lens, numeral 25 a blanker, numeral 26 a shutter valve, numeral 27 a variable opening, numeral 28 an octapole stigmator, numeral 29 an objective lens, numeral 30 an X-Y deflector, numeral 31 a gas gun, numeral 32 a sample, numeral 33 a sample stage, numeral 34 a high voltage source, numeral 35 an ion optical system controller, numeral 36 a blanking amplifier, numeral 37 a scan controller, numeral 38 a gas gun controller, numeral 39 a secondary electron detector, numeral 40 an amplifier, numeral 41 a CRT, numeral 42 a stage driver, numeral 43 a stage controller, and numeral 44 a controlling computer system.
In this type of focused ion beam apparatus having the above-mentioned structure, a liquid metal ion source, such as gallium, etc., is used as the ion source 21, and an emission current is detected by the beam monitor 23 in order to stabilize the beam. The ion beam 22 is focused by the condenser lens 24 and the objective lens 29 and irradiated onto the sample 32. The variable opening 27 is used to change the beam current. By operating the sample stage 33 and the X-Y deflector 30, the focused ion beam can be scanned across only a required area of the sample. In order to determine the location at which treatment is required, secondary electrons generated from the sample by irradiating the ion beam thereon are detected by the secondary electron detector 39, and an image of the detected secondary electrons is displayed on the CRT 41. The image of the secondary electrons is inputted in the control computer system 44 which then registers several process conditions based on the image, thereby successively carrying out a series of processes.
This type of conventional focused ion beam apparatus, however, has a drawback. When a wiring pattern in an IC is changed or a probing pad is formed in an IC, the IC is then taken out of the vacuum chamber for function analysis by an external tester such as an EB tester. If the above process has to be repeated several times for, e.g., rearrangement of the wiring pattern, this process becomes time-consuming since it requires time for re-evacuation of the vacuum chamber, retreatment, reanalysis, etc.